This invention relates to a tool drive unit or chuck unit for the operating heads of automatic machine tools, designed to machine at variable speed with constant torque. This characteristic means that high torque can be transmitted to the tool at a low rpm, thus making the machine ideal for machining materials such as titanium.
Automatic machine tools are known which comprise an operting head consisting of a fork fitted at the end of a mobile arm according to a number of axes, to which a chuck unit comprising a chuck and the equipment designed to rotate it are hinged.
Italian patent application 44804 A/88 describes an operating head of this type, which includes equipment designed to control limited movements of the chuck along its own axis as it rotates.
This system presents some limitations, however, in particular when titanium parts need to be machined, as this metal requires a low tool speed.
Known apparatus can only transmit sufficient power to the tool when it rotates at a high rpm.
For this reason there is a need for apparatus which enables constant torque to be transmitted to the chuck at any rpm.
This apparatus should preferably enable a number of speed ratios to be used, though without loss of precision, while maintaining the compactness achieved in current similar, more highly perfected types of apparatus.